Olokargh

"What do you mean don't go in the house?... There's a what in the house?... Well, look-ARGHHHH!"

— Someone missing, presumed dead

It Begins With A Stone

Known for their ability to become the sanctuary of their prey, olokarghs are capable of shifting into nearly anything.
Their true form is rarely seen, but those who have witnessed it have described it as being a giant, wreathing mass of tentacles. Olokarghs feed on the unsuspecting calmness that most people experience during moments where they are simply confused by what someone else is saying. Though they prefer to feed on that clear emotional state, they can also simply eat the flesh of creatures that wander by when it is between dedicated hunts.
The process they go through in becoming a persons sanctuary begins with them shifting into a violently smaller form of themselves and becoming part of their home. Once part of it, even just a single brick of it, they expand from there, eventually consuming the entire home. It maintains every aspect of it, with the only suspicion that something may be off is that dust will be cleared from the house as long as it remains an olokargh.

It Ends With A Bang

It is possible to free your home of an olokargh, though it isn't necessarily an easy task. You need to find their origin, their entry point to becoming the house. Usually this is marked by a cavity that they create to be able to get to the inner section of their origin point. Once it is found, it has to be disconnected from the rest of the house, whether that is through removing it directly or not is up to the person doing the removal. After it has become disconnected, the olokargh will be cut off from the rest of the house and they will be locked into their origin point.
The origin point then needs to be either thrown into fire or water, either will work, and the olokargh will die. Should the water be shallow, there is a chance that the olokargh will survive its transition from the origin point back into its true form. Large lakes, oceans, or wells are preferable because of this.
Once an olokargh has been purged from a home, it will never return to it. However if it successfully devours its target, it will remain there until it has been purged, making it very dangerous for people to go through abandoned buildings, especially if they became abandoned under suspicious circumstances...